Abstract

Background: In this study, the effect of postoperative oral anticoagulation
on the false lumen patency of the distal aorta in patients with acute type A
aortic dissection was investigated.

Methods: Forty-one patients (32 male, 9 female; mean age 56.8±13.6
years; range, 30 to 84 years) who were diagnosed with acute type A aortic
dissection and underwent surgical treatment in our clinic, and whose
entire data of both control computed tomographic assessments and all
postoperative follow-up visits could be accessed were enrolled. The patients
were divided into two groups according to the type of surgical intervention
that was performed. Computed tomography imaging of the patients were
scanned and false lumen patency rates were evaluated. Besides oral
anticoagulation, preoperative, intraoperative, and postoperative risk factors
that may have affected false lumen patency secondary to acute type A
aortic dissection were evaluated and statistically analyzed.

Results: Twenty-one patients (51.2%) had concomitant hypertension. Thirty
five (85.4%) of the patients had the main symptom of angina. Sixteen patients
(39%) in Group 1 underwent ascending aortic replacement combined with
aortic valve replacement (Bentall procedure); while 25 patients (61%) in
Group 2 underwent isolated ascending aortic replacement. Mean follow-up
was 43.9±26.3 (range: 5-120) months. No statistically significant difference
was found between the study subgroups in any of the operation parameters
except for cardiopulmonary bypass time (p=0.035) and cross-clamp time
(p=0.002). Evaluation of the control contrast-enhanced tomographic
imaging of the patients showed false lumen patency in the thorax in
34 patients (82.9%) and in the abdominal region in 33 patients (80.5%).
When analyzing subgroups according to the type of surgical procedure,
or indirectly anticoagulant use, no statistically significant difference
was found in false lumen patency prevalence between the thoracic and
abdominal groups (p=0.534 and p=0.922).

Conclusion: No potential effect of postoperative anticoagulation on false
lumen patency was found in cases with acute type A aortic dissection.

Introduction

Real and false lumens may develop in patients
with acute type A aortic dissection (AAAD) due to
tearing of the aortic intima.[1-4] Such cases are treated
with ascending aortic replacement (AAR) surgery;
however additional aortic valve replacement (AVR)
procedure may be necessary in patients who require
anticoagulant therapy with warfarin sodium added
to their postoperative medications.[3-6] Since previous
studies have revealed the potential correlation between
false lumen patency (FLP) and rupture or widening of
the lesion, we evaluated the effect of postoperative oral
anticoagulation over FLP at thoracic and abdominal
aortic segments.

Methods

The medical records of patients admitted to our
institutes emergency department with symptoms of
aortic dissection, and who were surgically treated
between April 2000 and April 2010 in our clinic
after AAAD diagnosis according to transthoracic
echocardiography (TTE) and thoracoabdominal
contrast computed tomography (CT) evaluations were
reviewed retrospectively. Patients diagnosed with
DeBakey type 2 were excluded. A total of 41 patients
who survived (32 male, 9 female; mean age 56.8±13.6
years; range, 30 to 84 years) and had complete data of
medical records, outpatient follow-up visits, and control
CT scans were enrolled in this study. The study was
conducted in accordance with the methods described
adhered to tenets of the Declaration of Helsinki, and
the study protocol was approved by the Institutional
Ethics Committee (Approval number: 2010; 10-9.1/6).
This is a retrospective, non-comparative interventional
case series, and all of the patients consented to our
review of their medical records.

All participants of the study underwent surgical
treatment performed via median sternotomy. The right
subclavian artery was the route for arterial cannulation
in 31 patients (75.6%); however, the femoral artery
was used for arterial cannulation in 10 instable
patients (24.4%) that required acute intervention. Right
atrial venous cannulation was used in all patients.
Group 1 consisted of 16 patients (39%) who underwent
AAR combined with aortic root replacement and
mechanical AVR surgery (Bentall procedure); whereas
Group 2 consisted of the remaining 25 patients (61%)
who underwent AAR combined with aortic valve
resuspension surgery.

Antiaggregant medication with acetylsalicylic
acid and anticoagulation with warfarin sodium was
administered postoperatively in Group 1 patients;
while Group 2 patients received only antiaggregant medication postoperatively. The efficacy of
postoperative anticoagulation over FLP was evaluated
after screening FLP at both thoracic and abdominal
aortic segments in postoperative control contrast
CT scans of each patient. A patent false lumen
was defined in CT scans that depicted an obvious
contrast transmission towards the false lumen; a partial
thrombosis of the false lumen was defined in CT scans
that depicted a filling defect according to a thrombus
within the false lumen; and complete thrombosis of the
false lumen was defined in CT scans that depicted any
obvious contrast transmission towards the false lumen.
Diagnosis of a patent or partially thrombosed false
lumen was described as FLP; however, the presence
of complete thrombosis was described as closed false
lumen for further analysis.

The data were recorded on a computerized database
and analyzed using SPSS version 15.0 statistical
software (SPSS Inc., Chicago, Illinois, USA). After
normality was tested with Kolmogorov-Smirnov test,
chi-square and Fishers chi-square tests were used for
the statistical analysis of nominal data, Mann-Whitney
U test was used for the statistical analysis of numerical
data, and Spearmans Rho test was performed for the
bivariate correlation analysis. A probability value of
<0.05 was considered significant.

Results

Age and gender distribution as well as mean body
mass index (BMI) and follow-up time, presence of
concomitant diseases (such as diabetes mellitus,
hypertension, and chronic obstructive pulmonary
disease-COPD), main symptoms at the time of first
referral to the emergency department, and the period
between the onset of symptoms and operation were
given in Table 1.

No statistically significant difference was found
between the two subgroups of the study in any of the
operation parameters except in cardiopulmonary bypass
time (p=0.035) and cross-clamp time (p=0.002). There
was also no statistically significant difference in mean
entubation time, intensive care unit (ICU) stay, total
hospitalization time, and follow-up duration between
both groups. No statistically significant difference was
found in postoperative complication risks between the
two study subgroups classified according to performed
surgical procedure; which also means the administration
of postoperative oral anticoagulation. However, a
cerebrovascular accident and a severe nephrological
complication requiring hemodialysis were seen in one
(4%) and two (8%) patients, respectively in Group 2,
neurologic and nephrological complications did not occur in Group 1 patients (p=0.418 and p=0.246,
respectively). One patient in Group 1 (6.2%) and
four patients in Group 2 (16%) developed pneumonia
(p=0.352). Sepsis was seen in one patient in Group 1
(6.2%); however, it was not diagnosed in any patients
in Group 2 (p=0.478).

After screening control contrast CT scans of all
study participants, FLP was found in 34 (82.9%)
thoracic, and 33 (80.5%) abdominal aortic segments.
When detailed subgroup analysis was performed according to the administration of postoperative
oral anticoagulation related to the type of surgical
procedure, FLP at thoracic aortic segment was present
in 14 out of 16 patients (87.5%) who were prescribed
oral anticoagulation after they underwent Bentall
procedure with mechanical AVR surgery. Among
them, FLP at abdominal aortic segment was evident
in 13 patients (81.3%). However, FLP at thoracic aortic
segment was revealed in 20 out of 25 patients (80%)
without any need for postoperative oral anticoagulation as they underwent AAR surgery combined with aortic
valve resuspension procedure. Screening of abdominal
aortic segment with CT scans also revealed that FLP
was present in 80% of the patients in Group 2 (Table 2).
No statistically significant difference was found in
FLP for both thoracic and abdominal aortic segments
between study subgroups. Control contrast angio-CT
scans designating patent (Figure 1a), partial thrombosis
(Figure 1b), and complete thrombosis (Figure 1c) of
false lumens, as well as a false lumen that was found
closed at thoracic and patent at abdominal aortic
segments (Figure 1d) were presented in Figure 1.

Of the entire study population, only three patients
(7.3%) had closed false lumen both at thoracic and
abdominal aortic segments. The remaining 38 patients
were diagnosed with FLP at either thoracic or abdominal
aortic segments. Statistical analyses revealed no
significant difference between the presence of closed
false lumen and any of the following: age, gender,
concomitant diagnosis of diabetes or hypertension,
performed operation type, time period between the onset of symptoms and surgical intervention,
cardiopulmonary bypass time and cross-clamp time,
total circulatory arrest (TCA) time, mean TCA
temperature, total amount of requested cardioplegia
and blood product requirement, the overall need for
inotropic agents, total entubation time, incidence of
postoperative complications, as well as the total length
of hospitalization, and ICU stay. However, presence
of concomitant COPD and/or lower BMI were found
to be related with a closed false lumen in our study
population.

Discussion

Aortic dissection, which was firstly described
in literature 200 years ago, is the most common
catastrophic, mortal, and urgent disease of the aorta
with its incidence of 0.5-3/100000.[1-3] Excision of the
primary intimal tear is the aim of dissection surgeries.
Aortic valve interventions including AAR combined
with AVR, subtotal root replacement, David, Bentall,
Bio-Bentall, or Cabrol procedures may be required in
cases with dilated aortic root, tear involving coronary
cusps, or severe aortic valve deformation.[7-11] Etz et
al.[11] reported the surgical o utcomes of 5 97 patients
who underwent Bentall procedure, and reported
subgroup analysis showed that implanted aortic valve
type did not have any impact over their early and late
surgical outcomes, including patients aged between
50 and 70 years. The authors also concluded that Bentall
procedure with mechanical aortic valve implantation
was the gold standard surgical approach, even in the
elderly population. Considering the younger mean age
and higher life expectations of our study population,
we also performed Bentall procedure combined with
the implantation of mechanical aortic valve prosthesis
in all of our study participants diagnosed with aortic
dissection and concomitant aortic valve disorder.
Any valve sparing techniques or the implantation of
biological aortic valve grafts were not used in any of
our study patients.

Within 5-10 years after AAAD surgery,
approximately 10-40% of the treated patients require
reoperations for distal aortic segments; which may
also affect these patients survival.[12-14] The literature
defines age, presence of any novel neurological deficits
at the time of referral, and preoperative diagnosis
of thrombosis located in the ascending aorta are
defined as major risk factors for late term mortality
after AAAD surgery; furthermore, patency of false
lumen is also described as a surgical technique related
parameter for mortality in such patients.[14-20] The
literature reports the frequency of FLP after AAAD
surgery to be between 40% and 85%.[2,13,14,21] We a lso found FLP rates of 82.9% and 80.5% for thoracic
and abdominal aortic segments, respectively, in our
study population; which is consistent with the recent
literature.

Although FLP is defined as a major risk factor
for dilatation of the distal aorta and more severe lateterm
outcomes in many studies,[12-15,21] some authors
reported no significant correlations between FLP and
survival rate, as well as between FLP and the need
for any aortic reoperations when they compared those
with patients with a thrombosis of false lumen.[2,19]
In a study published in 2011, Song et al.[22] reported
lower frequencies of thrombotic complications and
malperfusion in patients with a partial thrombosis of
false lumen. Bernard et al.[15] published the impacts
of rapid enlargement of the lesion, advanced age, and
postoperative FLP over late-term aortic complications
as well as mortality. Some authors reported that annual
dilatation rate of aortic diameter was found to be
higher in cases with either patent or partial thrombosis
of false lumens when compared to those with a
thrombosis.[2,20,22] Fattouch et a l.[23] reported annual
aortic diameter enlargement rates of 2.8±0.4 mm
and 1.1±0.2 mm in cases with patent and false lumen
thrombosis, respectively. Fattori et al.[21] also found
these rates as 3.7 mm and 1.1 mm, respectively.
Furthermore, Sakaguchi et al.[24] reported increased
probability of FLP in cases with preoperatively
diagnosed hypertension and in those with preoperative
descending thoracic aortic diameter of ≥35 mm.
Reeger et al.[20] found increased probability for a false
lumen thrombosis in females, cases with lower body
surface area (BSA), and those with preoperative higher
EuroSCORES; however, young males were found to
be more prone to FLP. We did not find any correlation
between FLP and any of the following: age, gender,
concomitant diagnosis of diabetes or hypertension,
performed operation type, length of time between
the onset of symptoms and surgical intervention,
cardiopulmonary bypass time and cross-clamp time,
TCA time, mean TCA temperature, total amount of
requested cardioplegia and transfusion requirement,
the overall need for inotropic agents, total intubation
time, incidence of postoperative complications, as
well as the durations of total hospitalization, and ICU
stay. However, increased probability for a closed false
lumen was found in patients with comorbid COPD
in our study population. Higher rates of false lumen
thrombosis was also found to be frequent in those with
lower BMI and/or BSA; which was consistent with the
results of Reeger et al.[20]

Recent literature has suggested that oral
anticoagulation associated with mechanical valve surgeries or any other interventions may have an effect
over FLP.[22,25,26] In a study published in 2007, Gariboldi
et al.[25] reported higher probability of FLP in patients
who took anticoagulant medication postoperatively.
The authors stated that these were the results of
univariable analysis; however multivariable analysis
revealed no correlation between oral anticoagulation
and FLP. Moreover, they did not find any impact of
oral anticoagulation on the need for reoperation of
the distal aorta. In accordance with the results of
von Kodolitsch et al.,[19] we a lso found no statistically
significant correlation between postoperative oral
anticoagulation and FLP in our study population.

In accordance with the literature, the early and
mid-term surgical outcomes after aortic root and
valve replacement with mechanical valve prosthesis
were considerably gratifying in our younger patients
with AAAD and widened aortic root; which was
commonly associated with Marfans syndrome. Since
the reoperation of aortic valve and root may carry
significant morbidity and mortality risks in these
patients, the outcomes of surgical interventions without
any need for postoperative oral anticoagulation are
still doubtful as increased risk of early aortic valve
insufficiency may be evident secondary to valve
surgery approaches except from the implantation of
mechanical valve prosthesis.

In conclusion, the potential causes of false lumen
patency after an acute type A aortic dissection surgery
and the effect of oral anticoagulation over false lumen
patency are still not well known. We could not find
any potential effects of postoperative anticoagulation
over false lumen patency in patients with acute type A
aortic dissection.

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to
the authorship and/or publication of this article.

Funding
The authors received no financial support for the research
and/or authorship of this article.

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